// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_JOINT_H
#define B2_JOINT_H

#include "b2_api.h"
#include "b2_math.h"

class b2Body;
class b2Draw;
class b2Joint;
struct b2SolverData;
class b2BlockAllocator;

enum b2JointType
{
  e_unknownJoint,
  e_revoluteJoint,
  e_prismaticJoint,
  e_distanceJoint,
  e_pulleyJoint,
  e_mouseJoint,
  e_gearJoint,
  e_wheelJoint,
    e_weldJoint,
  e_frictionJoint,
  e_ropeJoint,
  e_motorJoint
};

struct B2_API b2Jacobian
{
  b2Vec2 linear;
  float angularA;
  float angularB;
};

/// A joint edge is used to connect bodies and joints together
/// in a joint graph where each body is a node and each joint
/// is an edge. A joint edge belongs to a doubly linked list
/// maintained in each attached body. Each joint has two joint
/// nodes, one for each attached body.
struct B2_API b2JointEdge
{
  b2Body* other;			///< provides quick access to the other body attached.
  b2Joint* joint;			///< the joint
  b2JointEdge* prev;		///< the previous joint edge in the body's joint list
  b2JointEdge* next;		///< the next joint edge in the body's joint list
};

/// Joint definitions are used to construct joints.
struct B2_API b2JointDef
{
  b2JointDef()
  {
    type = e_unknownJoint;
    bodyA = nullptr;
    bodyB = nullptr;
    collideConnected = false;
  }

  /// The joint type is set automatically for concrete joint types.
  b2JointType type;

  /// Use this to attach application specific data to your joints.
  b2JointUserData userData;

  /// The first attached body.
  b2Body* bodyA;

  /// The second attached body.
  b2Body* bodyB;

  /// Set this flag to true if the attached bodies should collide.
  bool collideConnected;
};

/// Utility to compute linear stiffness values from frequency and damping ratio
B2_API void b2LinearStiffness(float& stiffness, float& damping,
  float frequencyHertz, float dampingRatio,
  const b2Body* bodyA, const b2Body* bodyB);

/// Utility to compute rotational stiffness values frequency and damping ratio
B2_API void b2AngularStiffness(float& stiffness, float& damping,
  float frequencyHertz, float dampingRatio,
  const b2Body* bodyA, const b2Body* bodyB);

/// The base joint class. Joints are used to constraint two bodies together in
/// various fashions. Some joints also feature limits and motors.
class B2_API b2Joint
{
public:

  /// Get the type of the concrete joint.
  b2JointType GetType() const;

  /// Get the first body attached to this joint.
  b2Body* GetBodyA();

  /// Get the second body attached to this joint.
  b2Body* GetBodyB();

  /// Get the anchor point on bodyA in world coordinates.
  virtual b2Vec2 GetAnchorA() const = 0;

  /// Get the anchor point on bodyB in world coordinates.
  virtual b2Vec2 GetAnchorB() const = 0;

  /// Get the reaction force on bodyB at the joint anchor in Newtons.
  virtual b2Vec2 GetReactionForce(float inv_dt) const = 0;

  /// Get the reaction torque on bodyB in N*m.
  virtual float GetReactionTorque(float inv_dt) const = 0;

  /// Get the next joint the world joint list.
  b2Joint* GetNext();
  const b2Joint* GetNext() const;

  /// Get the user data pointer.
  b2JointUserData& GetUserData();

  /// Short-cut function to determine if either body is enabled.
  bool IsEnabled() const;

  /// Get collide connected.
  /// Note: modifying the collide connect flag won't work correctly because
  /// the flag is only checked when fixture AABBs begin to overlap.
  bool GetCollideConnected() const;

  /// Dump this joint to the log file.
  virtual void Dump() { b2Dump("// Dump is not supported for this joint type.\n"); }

  /// Shift the origin for any points stored in world coordinates.
  virtual void ShiftOrigin(const b2Vec2& newOrigin) { B2_NOT_USED(newOrigin);  }

  /// Debug draw this joint
  virtual void Draw(b2Draw* draw) const;

protected:
  friend class b2World;
  friend class b2Body;
  friend class b2Island;
  friend class b2GearJoint;

  static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
  static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);

  b2Joint(const b2JointDef* def);
  virtual ~b2Joint() {}

  virtual void InitVelocityConstraints(const b2SolverData& data) = 0;
  virtual void SolveVelocityConstraints(const b2SolverData& data) = 0;

  // This returns true if the position errors are within tolerance.
  virtual bool SolvePositionConstraints(const b2SolverData& data) = 0;

  b2JointType m_type;
  b2Joint* m_prev;
  b2Joint* m_next;
  b2JointEdge m_edgeA;
  b2JointEdge m_edgeB;
  b2Body* m_bodyA;
  b2Body* m_bodyB;

  int32 m_index;

  bool m_islandFlag;
  bool m_collideConnected;

  b2JointUserData m_userData;
};

inline b2JointType b2Joint::GetType() const
{
  return m_type;
}

inline b2Body* b2Joint::GetBodyA()
{
  return m_bodyA;
}

inline b2Body* b2Joint::GetBodyB()
{
  return m_bodyB;
}

inline b2Joint* b2Joint::GetNext()
{
  return m_next;
}

inline const b2Joint* b2Joint::GetNext() const
{
  return m_next;
}

inline b2JointUserData& b2Joint::GetUserData()
{
  return m_userData;
}

inline bool b2Joint::GetCollideConnected() const
{
  return m_collideConnected;
}

#endif
